1. Field
This invention relates to link physical error detection, and more specifically to minor link physical error detection using sliding window methodology.
2. Background
In data transfers across a link between two nodes, many network protocols require the detection of physical or bit errors as an indication of link data integrity. An extensive number of physical errors indicate the link integrity is questionable. Interactions from the devices communicating across this link may be required to test and correct the link data integrity.
The Infiniband (IBA) protocol defines minor link physical errors to be occurrences of specific events that may jeopardize link quality. An Infiniband port may utilize either a single or double pumped data stream. It is the responsibility of all devices connected through an Infiniband protocol to monitor the occurrences of these events and to use this information to gauge current network quality. If during network operation, the network quality falls below a pre-described amount, the link between the two nodes is retrained. The Infiniband specification defines several events the occurrence of which may be considered minor link physical error events for an Infiniband link. These include: invalid 8B/10B code groups and running disparity errors; unsupported or disabled valid code groups; any control symbol within the boundaries of a packet; pad symbols on a non-12x link; start or end packet delimiter in wrong lane of multi lane link; or on a 12x link, PAD symbols not preceded by end of packet delimiter.
If any of these minor link physical error events occur, retraining may need to be performed to get the two nodes back into synchronization. During retraining, a data pattern may be sent from one node to a second node. The second node may receive the data pattern and then send another data pattern in response. This may continue between the links for a certain time until they both agree and arrive that the link is in a good state. The link may now be used for other information traffic outside of link training.
The Infiniband specification describes two link physical error threshold algorithms for tracking these occurrences. One of these algorithms is the sliding window algorithm. Under the sliding window algorithm, logic tracks the minor error status of the most recent sixteen symbol times. Moreover, an error threshold event may be reported when four or more minor errors are present within the sixteen most recent symbol times of history.
Therefore, a need exists for method and apparatus for minor link physical error tracking that implements a sliding window algorithm, and may be used with a single pumped or double pumped data stream, and also tracks minor link physical errors that may be misaligned with a symbol clock.